Kevin_Z wrote

@Julian_N 

 

Do you mean this issue occurs after you updated the Windows 10 system? Is there any setting related to the second monitor on the Windows 10?

 

What if you unplug this T6E from the Windows 10, leave it connect to the router with an Ethernet, will it work properly with the second monitor enabled?

 

Thanks for the reply. 

Yes, this issue started after a Windows 10 update, around October, before that it was working fine.

I can't test with an Ethernet, because I don't have a cable long enough to reach it. 
I already tested using an old USB Wifi adapter (which is also a TP-Link product, model TL-WN821N) and the problem did not occurred.
That why I don't think there is a problem with any configuration with the second monitor.

I also have 2 other notebooks and 2 smartphones connected to this router, and their speed is normal.

It seems that in this other thread, some users have a similar problem with a second monitor and higher resolution.
https://community.tp-link.com/en/home/forum/topic/204498?page=3

I ran some tests based on the above thread:

-Main Monitor (1920x1080):

Protocol:    Wi-Fi 4 (802.11n)
Bandwidth:    5 GHz
Channel:    157
Connection speed (Rx/Tx):    866/866 (Mbps)
Manufacturer:    TP-Link
Description:    TP-Link 802.11ac Network Adapter
Driver version:    6.30.223.228
Speed Test: 110Mbps

I tried to force connection to a 5GHz, but as soon as I change the monitor settings to Dual or Second monitor, the 5GHz just vanishes.
If I revert the config to the main monitor, it shows again.

- Second monitor only (tested with resolution 2560X1080 and 1920x1080):
Bandwidth:    2,4 GHz
Channel:    10
Connection speed (Rx/Tx):    866/39 (Mbps)
Speed test: 980Kbps (yes it's Kbps)

- Dual monitor:
Bandwidth:    2,4 GHz
Channel:    2
Connection speed (Recepção/Transmissão):    866/144 (Mbps)
Speed test: 6.1Mbps

I omitted the fields that were the same as the main monitor.